The NIH is one of eight centers in this prospective, multi-center, double-blind, randomized, placebo-controlled study. The objective is to determine the safety and efficacy of nitric oxide for inhalation in the treatment of vaso-occlusive pain crisis in patients with sickle cell disease. The study population will include patients with sickle cell disease (SS, S-beta-Thalassemia) presenting with vaso-occlusive pain crisis. Patients will be 10 years of age or above and will be administred either placebo or inhaled nitric oxide to see if the experimental agent, inhaled nitric oxide, can reduce the time it takes for resolution of the vaso-occlusive crisis. We began pre-enrolling in January 2005 and to date have pre-enrolled 86 subjects. Of these 86 subjects, 30 have actually enrolled and been randomized to either placebo or nitirc oxide and an additional 9 more subjects who were not pre-enrolled have also been randomized in the study bringing the total number of subjects at the NIH randomized to the study to 39. Of these 39 subjects, 2 have been children. We anticipate pre-enrolling approximately 200 subjects and enrolling and randomizing 50 of the pre-enrolled subjects. Due to the double-blind nature and the design of this trial, no preliminary data analysis will be available until completion of the entire study.[unreadable] [unreadable] The other participating sites have also began enrollment. This brings the number of subjects pre-enrolled to 136 and the number of subjects randomized in the treatment study to 95.[unreadable] [unreadable] This protocol has been reviewed by the Pulmonary DSMB of the NHLBI 6 times and has consistently been recommended for continuation. The DSMB has reviewed the unblinded Serious Adverse Events and the methemoglobin values of all subjects enrolled as of May 2007 and no safety concerns were appreciated at that time.